Field of the Disclosure
The present disclosure relates to nanomaterials. More specifically, the present disclosure relates to a flexible, transparent nanomesh for conductive coatings.
Background of the Technology
With the rapid development of photo-electronics, there is an increasing demand for improved performance and wider application of flexible transparent electrodes. For example, the market for touch screen and foldable display technologies that rely on flexible transparent electrodes continues to grow. Additionally, epidermal electronics represent an emerging application for electrodes with high flexibility.
Transparent, flexible materials including carbon nanotubes, graphene, and metal nanowires are being investigated to replace transparent conductive electrodes such as tin doped indium oxide or indium-tin-oxide (ITO) films. Carbon nanotube and graphene electrodes present a good transmittance of around 80%, but they have a sheet resistance that is greater than about 100Ω/□ (ohms per square). The resistance of these carbon meshes is too high for many photo-electronic applications. In contrast, metal nanomeshes, usually silver (Ag) may achieve high electrical conductivity and demonstrate transparency comparable to indium-tin-oxide (ITO) films. Generally, metal nanomeshes are fabricated by two processes. First, utilizing any of the well-established/conventional, expensive nanofabrication techniques such as electron beam lithography, focused ion beam milling, and nanoimprint lithography, which enable fine features on a sub-100 nm scale. Alternatively, there is a solvent route that can make metal nanowires, such as the aforementioned Ag, at comparatively lower cost and higher throughput. The nanowires produced thusly have a length of between about 1 μm and about 10 μm, and a diameter between about 50 nm and about 100 nm. These nanowires may be assembled to form a random metal mesh electrode. However, the electrical properties of a metal mesh electrode produced accordingly are comparable to conventional nanofabrication techniques, due in-part to the non-uniformity and high resistance of the contacting junction between metal nanowires. While annealing is effective to decrease the junction resistance, it is not compatible with many organic substrates and therefore not suitable for flexible electronics. In some cases, the use of ultralong nanowires can significantly improve conductivity, but the synthesis is more complicated and, in certain instances, the solution-processed Ag nanowires also yield high surface roughness.